1. Technical Field
The present disclosure relates to a fingerprint sensor and a display device including the same.
2. Discussion of the Related Art
As computer technology advances, computer-based systems for various purposes, such as a notebook computer, a tablet PC, a smart phone, a personal digital assistant, an automated teller machine, and a search guide system, have been developed. Security for these systems needs to be enhanced in order to protect information or data stored in the systems because such information or data may include, e.g., personal information related to private life, and/or business information or business secrets, which require confidentiality.
To this end, there has been generally known a fingerprint sensor capable of enhancing security by performing system registration or authentication using the fingerprint of a finger. The fingerprint sensor detects the fingerprint of a finger of a person. The fingerprint sensor types are an optical fingerprint sensor and a capacitive fingerprint sensor.
The optical fingerprint sensor is based on the principle in which an internal light-emitting diode (LED) radiates a light source, and then light reflected by the ridges of a fingerprint is detected by a CMOS image sensor. The optical fingerprint sensor is limited in its ability to reduce the size because the scan needs to be performed using an LED. Also, the optical fingerprint sensor is problematic in that a manufacturing cost is increased because the light source, itself, is expensive.
In the capacitive fingerprint sensor, a difference in the amount of electricity charged between ridges which touch the fingerprint sensor and valleys is used. Known capacitive fingerprint sensors include U.S. Patent Application Publication No. 2013/0307818 (“the '818 application”), published on Nov. 21, 2013, entitled “Capacitive Sensor Packaging.” The capacitive fingerprint sensor disclosed in the '818 application includes a specific push button combined with the sensor in an assembly form and a silicon wafer on which a circuit for measuring capacitance between a capacitive plate and the fingerprint (i.e., ridges and valleys) of a user has been printed.
In general, a ridge and valley of the fingerprint of a human being is very fine, that is, 300 μm˜500 μm in size. In the capacitive fingerprint sensor disclosed in the '818 application, a high-resolution sensor array and an integrated chip (IC) for fingerprint recognition and processing need to be fabricated. To this end, the silicon wafer in which the sensor array and the IC are integrated is used.
If the high-resolution sensor array and the IC are integrated using the silicon wafer, however, there are problems in that the configuration becomes complicated, and a non-display area (i.e., a bezel area) size is increased because an assembly structure for coupling the fingerprint sensor and the push button is necessary. Furthermore, there are problems in that the thickness is increased and a fingerprint sensing area depends on the size of the push button because the push button (e.g., the home key of a smart phone) and the fingerprint sensor overlap.
In order to solve such problems, a technology using the area of a touch sensor screen as a fingerprint identification area has been developed. Such a technology includes U.S. Pat. No. 8,564,314 (“the '314 patent”), issued on Oct. 22, 2013, entitled “Capacitive Touch Sensor for Identifying a Fingerprint” and Korean Patent No. 10-1432988 (“the '988 patent”), issued on Aug. 18, 2014, entitled “Fingerprint Recognition-Integrated Type Capacitance Touch Screen.”
FIG. 1 of the present disclosure corresponds to FIG. 5 of the '314 patent and is a plan view schematically showing the array of the driving electrodes and sensing electrodes of a related art capacitive sensing panel. FIG. 2 of the present disclosure corresponds to FIG. 3 of the '988 patent and is a plan view showing the configuration of a related art fingerprint recognition-integrated type capacitance touch screen panel.
With reference to FIG. 1 of the present disclosure, a capacitive touch sensor for fingerprint identification includes a touch sensor 403 including touch driving electrodes 401(x) and touch sensing electrodes 401(y) and a fingerprint sensor 405 including fingerprint driving electrodes 405(x) and fingerprint sensing electrodes 405(y). However, the capacitive sensing panel has a problem in that the area of the fingerprint sensor 405 is not touched or touch performance in the surrounding area of the fingerprint sensor 405 is low because the separate fingerprint sensor 405 is partially disposed in the screen (display) area of the capacitive touch sensor.
With reference to FIG. 2, the fingerprint recognition-integrated type capacitance touch screen includes a touch panel 110, electrode connection lines 120, and a touch controller 130. In the configuration of FIG. 2, the touch panel 110 includes fine channels 113, each formed by a combination of a first channel electrode 111 (Tx or Rx), and a second channel electrode 112 (Tx or Rx) arranged to cross each other. Fine channels 113 that belong to the fine channels 113 and that are disposed in the remaining areas other than the area of a fingerprint recognition sensor 114 are plurally grouped and function as touch group channels 115 for detecting a touch signal. Each of the fine channels 113 disposed in the area of the fingerprint recognition sensor 114 functions as a fingerprint recognition channel 116. In the fingerprint recognition-integrated type capacitance touch screen, however, mutual capacitance between the fine channels 113 (i.e., touch channels) is greatly increased due to the touch channels functioning as the touch group channels 115. Accordingly, there is a problem in that a touch is not recognized when a touch operation is generated because such an increase of mutual capacitance causes deterioration of the sensing sensitivity of the touch sensor.